#region License

/*
 * Copyright ?2002-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#endregion

#region Imports

using System;
using System.Collections;
using System.Collections.Specialized;

using Spring.Util;

#endregion

namespace Spring.Core.TypeResolution
{
    /// <summary>
    /// Resolves (instantiates) a <see cref="System.Type"/> by it's (possibly
    /// assembly qualified) name, and caches the <see cref="System.Type"/>
    /// instance against the type name.
    /// </summary>
    /// <author>Rick Evans</author>
    /// <author>Bruno Baia</author>
    /// <author>Erich Eichinger</author>
    public class CachedTypeResolver : ITypeResolver
    {
        /// <summary>
        /// The cache, mapping type names (<see cref="System.String"/> instances) against
        /// <see cref="System.Type"/> instances.
        /// </summary>
        private readonly IDictionary typeCache = new HybridDictionary();

        private readonly ITypeResolver typeResolver;

        /// <summary>
        /// Creates a new instance of the <see cref="Spring.Core.TypeResolution.CachedTypeResolver"/> class.
        /// </summary>
        /// <param name="typeResolver">
        /// The <see cref="Spring.Core.TypeResolution.ITypeResolver"/> that this instance will delegate
        /// actual <see cref="System.Type"/> resolution to if a <see cref="System.Type"/>
        /// cannot be found in this instance's <see cref="System.Type"/> cache.
        /// </param>
        /// <exception cref="System.ArgumentNullException">
        /// If the supplied <paramref name="typeResolver"/> is <see langword="null"/>.
        /// </exception>
        public CachedTypeResolver(ITypeResolver typeResolver)
        {
            AssertUtils.ArgumentNotNull(typeResolver, "typeResolver");
            this.typeResolver = typeResolver;
        }

        /// <summary>
        /// Resolves the supplied <paramref name="typeName"/> to a
        /// <see cref="System.Type"/>
        /// instance.
        /// </summary>
        /// <param name="typeName">
        /// The (possibly partially assembly qualified) name of a
        /// <see cref="System.Type"/>.
        /// </param>
        /// <returns>
        /// A resolved <see cref="System.Type"/> instance.
        /// </returns>
        /// <exception cref="System.TypeLoadException">
        /// If the supplied <paramref name="typeName"/> could not be resolved
        /// to a <see cref="System.Type"/>.
        /// </exception>
        public Type Resolve(string typeName)
        {
            if (StringUtils.IsNullOrEmpty(typeName))
            {
                throw BuildTypeLoadException(typeName);
            }
            Type type = null;
            try
            {
                lock (this.typeCache.SyncRoot)
                {
                    type = this.typeCache[typeName] as Type;
                    if (type is null)
                    {
                        type = this.typeResolver.Resolve(typeName);
                        this.typeCache[typeName] = type;
                    }
                }
            }
            catch (Exception ex)
            {
                if (ex is TypeLoadException)
                {
                    throw;
                }
                throw BuildTypeLoadException(typeName, ex);
            }
            return type;
        }

        private static TypeLoadException BuildTypeLoadException(string typeName)
        {
            return new TypeLoadException("Could not load type from string value '" + typeName + "'.");
        }

        private static TypeLoadException BuildTypeLoadException(string typeName, Exception ex)
        {
            return new TypeLoadException("Could not load type from string value '" + typeName + "'.", ex);
        }

        public bool TryResolve(string typeName, out Type type)
        {
            type = null;
            if (StringUtils.IsNullOrEmpty(typeName))
            {
                return false;
            }
            try
            {
                lock (this.typeCache.SyncRoot)
                {
                    type = this.typeCache[typeName] as Type;
                    if (type is null)
                    {
                        if (this.typeResolver.TryResolve(typeName, out type) && type is not null)
                        {
                            this.typeCache[typeName] = type;
                        }
                    }
                    return type is not null;
                }
            }
            catch
            {
                return false;
            }
        }
    }
}
